The invention generally relates to the field of fault classification. More particularly, the invention relates to classifying crossover faults on power lines.
The operation of every electrical power transmission system requires the proper handling of electrical faults that occasionally occur. Such faults stem from a variety of events including lightning strikes, stray animals, and falling branches, for example. In order to return the power system to proper operation, certain characteristics of the fault must be determined. For example, the location and severity of the fault is essential to clearing the fault so that the power system can resume normal operation.
There are a number of different types of faults that may occur, such as phase-to-ground fault, phase-to-phase fault, and crossover faults. Phase-to-ground and phase-to-phase faults describe fault conditions that occur between conductors of the same circuit. Crossover faults, on the other hand, describe a fault condition that occurs between conductors of different circuits. The different circuits may or may not be in parallel (i.e., carrying power to and from the same locations). Classifying the type of fault also may be important in taking proper action to restore the power system to normal operation. For example, classifying a fault may enhance protection schemes by preventing the mistaken protection of just one of the two crossover-faulted circuits. Also, incorporating the type of fault into fault location algorithms can enhance the fault-locating techniques.
Recently, the classification of faults, and crossover faults in particular, has become increasingly more important as land restrictions and aesthetic concerns have limited the use of high voltage transmission lines, thus requiring that existing electrical towers be used to carry multiple circuits, in lieu of building new towers. To date, the classification of faults has been accomplished using multi-terminal techniques. For example, for crossover faults both three-phase circuits must be monitored in order to classify the fault as a crossover fault. However, this is especially difficult with crossover faults because, as mentioned, the different circuits involved in the crossover fault may not start and end at the same location (i e., the circuits are not in parallel). Therefore, complicated communication networks must be used to bring the data to a central location. Moreover, as may be expected, coordinating data between two different circuits (even where the circuits are in parallel) is inherently more complicated than simply monitoring one circuit.
Therefore, a need exists to classify crossover faults by monitoring one of the affected conductors in the electric power transmission system.
The invention describes a method, device, system, and computer-readable medium having computer-executable instructions for classifying faults on an electrical power line. In particular, the invention permits the classification of crossover faults (commonly referred to as faults that involve multiple circuits), using a local measurement technique. By distinguishing between crossover faults and other faults, the invention permits a more efficient and effective return of the power system to normal operation.
The inventive method includes providing a first electrical power transmission line and a second electrical power transmission line, and monitoring the first electrical power transmission line to identify a crossover fault occurring between the first and the second electrical power transmission lines. For example, one method for classifying faults on an electrical power line analyzes the phase relationships between the positive and negative-sequence voltage drops on a circuit. In particular, the invention may measure a fault and prefault electrical characteristic (e.g., current and/or voltage) on the first electrical power line. The method may determine a positive-sequence component for the fault and prefault electrical characteristics, and a negative-sequence component for the fault and prefault electrical characteristics. The method may then calculate a positive-sequence difference between the positive-sequence components of the fault and prefault electrical characteristics, and calculate a negative-sequence difference between the negative-sequence components of the fault and prefault electrical characteristics. The method may then calculate a first difference between a phase angle of the positive-sequence difference and a phase angle of the negative-sequence difference. The method further may include identifying that the fault is a crossover fault, a single-phase-to-ground fault, and/or a fault is not a phase-to-phase fault. The inventive method may act to correct the fault as a function of the classifying, and/or identify a location of the fault as a function of the classifying. The above method may be conducted by computer-executable instructions located on a computer-readable medium.
The inventive device includes a first input for receiving electrical power from a first part of an electrical transmission line, and a second input for receiving electrical power from a second part of an electrical transmission line. The device further includes a processor component for classifying faults on an electrical power line, where the processor performs the method described above.
The foregoing and other aspects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.